If a request already in the queue is passed to tegra_dma_enqueue_req,
tegra_dma_req.node->{next,prev} will end up pointing to itself instead
of at tegra_dma_channel.list, which is the way a the end-of-list
should be set up. When the DMA request completes and is list_del'd,
the list head will still point at it, yet the node's next/prev will
contain the list poison values. When the next DMA request completes,
a kernel panic will occur when those poison values are dereferenced.
This makes the DMA driver more robust in the face of buggy clients.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Colin Cross <ccross@android.com>
Sometimes, due to high interrupt latency in the continuous mode
of DMA transfer, the half buffer complete interrupt is handled
after DMA has transferred the full buffer. When this is detected,
stop DMA immediately and restart with the next buffer if the next
buffer is ready.
originally fixed by Victor(Weiguo) Pan <wpan@nvidia.com>
In place of using the simple spin_lock()/spi_unlock() in the
interrupt thread, using the spin_lock_irqsave() and
spin_unlock_irqrestore(). The lock is shared between the normal
process context and interrupt context.
originally fixed by Laxman Dewangan (ldewangan@nvidia.com)
The use of shadow registers caused memory corruption at physical
address 0 because the enable bit was not shadowed, and assuming it
needed to be set would enable an unconfigured dma block. Most of the
register accesses don't need to know the previous state of the
registers, and the few places that do need to modify only a few bits
in the registers are the same ones that were sometimes incorrectly
setting the enable bit. This patch convert tegra_dma_update_hardware
to set the entire register, and the other users to read-modify-write,
and drops the shadow registers completely.
Also fixes missing locking in tegra_dma_allocate_channel
Signed-off-by: Colin Cross <ccross@android.com>
The APB DMA block handles DMA transfers to and from some peripherals
in the Tegra SOC. It reads from sequential addresses on the memory
bus, and writes repeatedly to the same address on the APB bus.
Two transfer modes are supported, oneshot for transferring a known
size to or from a peripheral, and continuous for streaming data.
In continuous mode, a callback occurs when the buffer is half full
to allow the existing data to be handled and a new request queued.x
v2 changes:
dma API no longer uses PTR_ERR
Signed-off-by: Erik Gilling <konkers@android.com>
Signed-off-by: Colin Cross <ccross@android.com>
Stephen Warren
Colin Cross